Grounding cap module, gas injection device and etching apparatus

ABSTRACT

A grounding cap module includes a main body, a frame portion, and a cap portion. The main body includes a first opening penetrating the main body and a grounding portion disposed on a periphery of the main body and configured to be electrically grounded. The frame portion is disposed on the main body and includes a second opening aligned with the first opening. The cap portion is disposed on the frame portion and covers the second opening, wherein the first opening, the second opening and the cap portion define a receiving cavity. A gas injection device and an etching apparatus using the same are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application of patent application Ser. No.15/874,885, filed on Jan. 19, 2018, which claims the priority benefit ofU.S. provisional application Ser. No. 62/584,903, filed on Nov. 12, 2017and is now allowed. The entirety of the above-mentioned patentapplication is hereby incorporated by reference herein and made a partof this specification.

BACKGROUND

A photomask is used during the manufacture of an integrated circuit (IC)to transfer the design of each chip layer onto a semiconductorsubstrate. Since a photomask contains the pattern for a single layer ofthe chip, a set of 15 to 30 photomasks is typically used in theconstruction of a chip. Photomasks are reusable and typically comprise asubstrate, a reflective layer, and an absorber layer.

Extreme ultraviolet (EUV) lithography is a promising new patterningtechnology for producing very small (i.e. 14 nm) chips. EUV lithography,like optical lithography, uses a set of photomasks that reflect EUVlight to form a patterned photoresist on a semiconductor substrate.

Photomasks for EUV lithography are generally manufactured by etching thechip layer pattern into the photomask. This process has a low tolerancefor error, since any defects in the photomask will be transferred to thesemiconductor substrate during EUV lithography. To manufacture aphotomask, a substrate (e.g., quartz) is typically etched in an etchingchamber wherein a photomask can be exposed to various process gasses andplasmas.

Dry etching processes, also referred to as plasma etching processes, arecarried out to etch various films at various stages of the semiconductormanufacturing operation and produce various device features. Multipleplasma etching operations are generally required to form a semiconductordevice. One shortcoming of such plasma etching operations is thegeneration of polymers as etch by-products within the etching chamber.The polymers can adhere to various surfaces within the etch chamber andbecome dislodged, contaminating the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a schematic view of an etching apparatus according tosome exemplary embodiments of the present disclosure.

FIG. 2 illustrates a cross sectional view of a gas injection deviceaccording to some exemplary embodiments of the present disclosure.

FIG. 3 illustrates an exploded view of a grounding cap module accordingto some exemplary embodiments of the present disclosure.

FIG. 4 illustrates a schematic view of a grounding cap module accordingto some exemplary embodiments of the present disclosure.

FIG. 5 illustrates a perspective view of a part of the components of thegas injection device according to some exemplary embodiments of thepresent disclosure.

FIG. 6 illustrates a schematic view of a part of the components of thegas injection device according to some exemplary embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In addition, terms, such as “first,” “second,” “third,” “fourth,” andthe like, may be used herein for ease of description to describe similaror different element(s) or feature(s) as illustrated in the figures, andmay be used interchangeably depending on the order of the presence orthe contexts of the description.

FIG. 1 illustrates a schematic view of an etching apparatus according tosome exemplary embodiments of the present disclosure. FIG. 2 illustratesa cross sectional view of a gas injection device according to someexemplary embodiments of the present disclosure. Referring to FIG. 1 andFIG. 2 , in some embodiments, the etching apparatus 10 may be a plasmaetching apparatus (also referred to as dry etching apparatus) used inthe production of semiconductor components such as, but not limited to,semiconductor wafers. In some embodiments, the etching apparatus 10includes an etching chamber 200 defining a chamber cavity 210 and a gasinjection device 100 configured to supply process gas, e.g. oxygen or afluorine-bearing gas, into the etching chamber 200. Accordingly, theetching apparatus 10 is configured to produce a plasma from the processgas using a high frequency electric field. In detail, a semiconductorwafer may be placed in the etching chamber 200, and the air is evacuatedfrom the etching chamber 200 using, for example, a system of vacuumpumps. Then, the process gas is introduced at low pressure, and isexcited into a plasma through dielectric breakdown. In some embodiments,plasma etching processes, also referred to as dry etching processes, arecarried out to etch various films at various stages of the semiconductormanufacturing operation and produce various device features. Multipleplasma etching operations are generally required to form a semiconductordevice.

The etching apparatus 10 in the disclosure applies to varioussemiconductor wafer sizes and various semiconductor wafer materials uponwhich semiconductor devices are formed. Silicon and gallium arsenide areexamples of semiconductor wafer materials commonly used in today'ssemiconductor manufacturing industry. The grounding cap module 130 andthe gas injection device 100 of the disclosure applies to variousetching apparatus manufactured by various equipment manufacturers. Theetching apparatus 10 in the disclosure may be used in various types ofdry etching operations used to etch various films at various stages inthe semiconductor device manufacturing processing sequence.

In some embodiments, the etching apparatus 10 may further include a topelectrode 300 and a bottom electrode 400. The top electrode 300 isdisposed on the upper portion of the etching chamber 200, and theprocess gas provided by the gas injection device 100 is introduced tothe chamber cavity 210 through the top electrode 300. In someembodiments, the top electrode 300 may include a plurality of gas holespassing through the top electrode 300 for the process gas to passthereby. The bottom electrode 400 is disposed on the lower portion ofthe etching chamber 200. The top electrode 300 and the bottom electrode400 operate to incur a capacitive effect in the etching chamber 200.Herein, the process gas introduced to the etching chamber 200 is subjectto an electrochemical reaction and thereby ionized, transforming intoplasma. Thereby, the semiconductor wafer placed in the etching chamber200 is etched by the plasma and the portions without photoresist areremoved thereby. Then, the plasma and corroded substances may beexpelled to the exterior of the etching chamber 200 by an exhaust pump.

In some embodiments, the gas injection device 100 includes a mainconduit 110, a gas pipe 120 and a grounding cap module 130. The mainconduit 110 is connected to the etching chamber 200 and includes a gasinlet 112. The gas pipe 120 is connected to the gas inlet 112 of themain conduit 110 to inject process gas into the main conduit 110. Inother words, the main conduit 110 is in fluid communication with the gaspipe 120 through the gas inlet 112. In one of the implementations, thegas injection device 100 may include multiple gas pipes 120 respectiveconnected to different gas sources. Accordingly, the process gasinjected into the main conduit 110 is a gas mixture, which includes, forexample, an inert carrier gas, anhydrous reactive gas, and enablingchemical gas of an enabling chemical compound, etc.

In some embodiments, a source of the anhydrous reactive gas can beselected from reactive gas capable of providing a steady flow ofanhydrous halogen-containing gas, such as gaseous hydrogen fluoride, andhydrazine, ammonia, carbon dioxide and oxides of nitrogen, etc. Thehydrogen fluoride source may be supplied as a liquid in a cylinder, andthen evaporated at a temperature sufficient to ensure free flow of thegaseous hydrogen fluoride from the source. In general, the source ofhydrogen fluoride is maintained at a suitable temperature ensuring thatthe hydrogen fluoride is maintained in an anhydrous state.

In some embodiments, the inert carrier gas used in the etching apparatus10 may be any gas which is inert to the materials to be treated andwhich will remain in the gaseous phase under the process conditionspresent. Suitable gases include the noble gases, such as nitrogen,argon, neon, argon, helium, krypton and xenon, etc. The inert carriergas is used both in purging the gas injection device 100 and the etchingchamber 200 before and after the reaction procedure. A source of theenabling chemical gas of an enabling chemical compound may include, forexample, water vapor generation. The water source should be of highpurity, for example, deionized water. In addition to enabling chemicalssuch as water, and alcohols such as methanol, ethanol and isopropanol,other enabling chemicals may be used. The disclosure is not limitedthereto.

Accordingly, the mixed process gases are flowed into the etching chamber200 as to expose the film on the wafer to the diluted reactive gas, andthe small quantities of water vapor causes the reaction between theoxide film and the anhydrous reactive gas to be initiated and sustainedthrough duration of the etching process. The semiconductor wafermaterials which can be treated by the etching process can, generally, beany type of semiconductor material which will be unaffected by thehalogen-containing gaseous etchant medium. When the semiconductormaterial is a wafer to be processed in the manufacture of integratedcircuit chips, it will typically be composed of such materials assilicon, polysilicon, garnet, binaries such as gallium arsenide andindium phosphide, also ternaries such as CdHgTe, GaAlAs and GaInP, andquaternaries such as GaInAsP. Other substrate materials which may betreated by this etching, cleaning, and/or polishing process includestainless steel, quartz, aluminum, germanium, gallium and selenium.

In general, polymers as etch by-products can adhere to various surfaceswithin the etching chamber 200 and become dislodged, contaminating theetching chamber 200. Accordingly, in some embodiments, the gas pipe 120is electrically grounded so as to reduce the generation of polymers asetch by-products within the gas injection device 100 and the etchingchamber 200. In one of the implementations, the gas pipe 120 isconnected to a ground electrode 500 shown in FIG. 1 . In someembodiments, the main conduit 110 may include a shielding layer 116disposed on an inner wall of the main conduit 110 to reduce polymerresidue in the main conduit 110. In some circumstances, polymer residuesmay still accumulate on an upper portion of the main conduit 110, whichis located above the gas inlet 114. Such polymer residues may fall offfrom the top surface 114 and fall on devices being fabricated on thesemiconductor wafer, leading to a high number of defects in the devices.

Accordingly, in some embodiments, the grounding cap module 130 isdisposed on the top surface 114 of the main conduit 110, which islocated above the gas inlet 114. The grounding cap module 130 covers thetop surface 114 and includes a grounding portion 132 b, which isconnected to the gas pipe 120 to be electrically grounded. In someembodiments, the grounding portion 132 b may be fixed to the gas pipe120 by, for example, a screw, or any other suitable fasten means. Inaddition, the material of the grounding cap module 130 includes metal,such as silver, nickel, or other suitable metal material. With theconfiguration of the grounding cap module 130, the issue of polymerresidue accumulating on the top surface 114 of the main conduit 110 canbe resolved, and yield rates of the devices being fabricated on thesemiconductor wafer can be improved.

In some embodiments, the gas injection device 100 may further include anoptical window 140 for operators to look therethrough. The opticalwindow 140 is disposed on the top surface 114 of the main conduit 110.The optical window 140 is protruded from the top surface 114 of the mainconduit 110 and is made of, for example, sapphire. In other words, theoptical window 140 may be, but not limited thereto, a sapphire window.Accordingly, the grounding cap module 130 may include a receiving cavityR1 for receiving and covering the optical window 140.

FIG. 3 illustrates an exploded view of a grounding cap module accordingto some exemplary embodiments of the present disclosure. FIG. 4illustrates a schematic view of a grounding cap module according to someexemplary embodiments of the present disclosure. Referring to FIG. 3 andFIG. 4 , in some embodiments, the grounding cap module 130 may include amain body 132, a frame portion 134, and a cap portion 136. The main body132 include a first opening 132 a and the grounding portion 132 b asshown in FIG. 3 . The first opening 132 a penetrates the main body 132,and the grounding portion 132 b is disposed on a periphery of the mainbody 132. In other words, the grounding portion 132 b is protruded froman outer edge of the main body 110 and connected to the ground electrode500 through the gas pipe 120, such that grounding cap module 130 iselectrically grounded by the grounding portion 132 b. In someembodiments, the grounding portion 132 b may have a fastening hole hlfor a fastening means, such as a screw, to penetrate therethrough, so asto lock the grounding portion 132 b to the gas pipe 120.

In some embodiments, the frame portion 134 is disposed on the main body132 and includes a second opening 134 a as shown in FIG. 3 . The secondopening 134 a is aligned with the first opening 132 a. In the presentembodiments, the frame portion 134 may surround and stand on the part ofthe main body 132 around the first openings 132 a, and the side wall ofthe second opening 134 a is coplanar with the side wall of the firstopening 132 a. In one of the implementations, the first opening 132 aand the second opening 134 a may both be in circular shapes with thesame diameters. In such embodiments, the frame portion 134 may be in aring shape, but the disclosure is not limited thereto.

In some embodiments, the dimensions of the first opening 132 a and thesecond opening 134 a may be identical. In other embodiments, the depth(height) of first opening 132 a may be different from the depth (height)of the second opening 134 a. In other embodiments, the diameter of thefirst opening 132 a may also be different from the diameter of thesecond opening 134 a. In such embodiments, the side wall of the secondopening 134 a may not be coplanar with the side wall of the firstopening 132 a. It is noted that the shapes and the dimensions of thefirst opening 132 a and the second opening 134 a may be adjustedaccording to the shapes and the dimensions of the optical window 140,such that the optical window 140 can be fitted therein.

In some embodiments, the cap portion 136 is disposed on the frameportion 134 and covers the second opening 134 a. With suchconfiguration, the first opening 132 a, the second opening 134 a, andthe cap portion 136 can jointly define the receiving cavity R1, as shownin FIG. 2 , for receiving and covering the optical window 140. With suchconfiguration, the grounding cap module 130 can be applied to the gasinjection device 120 to meet the grounding requirement without alteringthe original structure of the gas injection device 120. Therefore, theissue of polymer residue accumulating on the top surface 114 of the mainconduit 110 can be resolved without altering the original configurationof the gas injection device 120, and yield rates of the devices beingfabricated on the semiconductor wafer can be improved.

In addition, the materials of the main body 132, the frame portion 134,and the cap portion 136 may include metal. In some embodiments, thematerials of the main body 132, the frame portion 134, and the capportion 136 may be the same and may include, but not limited thereto,silver, nickel, or any other suitable metal or alloy. In the presentembodiments, the grounding cap module 130 is made in a plurality ofseparate pieces (e.g. the main body 132, the frame portion 134, and thecap portion 136) for simplicity of manufacture of the grounding capmodule 130. Moreover, the production cost of the grounding cap module130 can be effectively reduced. Certainly, the disclosure is not limitedthereto. Alternatively, in other embodiments, the grounding cap modulecan be integrally formed. In other words, the grounding cap module canbe made in one piece with the grounding portion 132 b extended to thegas pipe 120 to be electrically grounded, and the one-pieced groundingcap module may have the receiving cavity R1 for receiving the opticalwindow 140.

FIG. 5 illustrates a perspective view of a part of the components of thegas injection device according to some exemplary embodiments of thepresent disclosure. FIG. 6 illustrates a schematic view of a part of thecomponents of the gas injection device according to some exemplaryembodiments of the present disclosure. Referring to FIG. 5 and FIG. 6 ,in some embodiments, the gas injection device 100 may further include acover plate 150, which is disposed on the main body 132 of the groundingcap module 130. The cover plate 150 includes a through hole 152 as shownin FIG. 5 . The cap portion 136 and the frame portion 134 are fitted inthe through hole 152 as shown in FIG. 2 and FIG. 5 . In someembodiments, originally, the through hole 152 of the cover plate 150 isconfigured to receive the optical window 140, but, now that the opticalwindow 140 is received by the grounding cap module 130, the through hole152 is configured to receive the grounding cap module 130 and theoptical window 140 therein as shown in FIG. 2 .

In some embodiments, the cover plate 150 may be fixed to the top surfaceof the main conduit 110 by a plurality of fastening components 170 suchas, but not limited to, screws. In the present embodiment, the coverplate 150 may include a plurality of fastening holes 154 as shown inFIG. 5 . Correspondingly, the main body 132 may include a plurality offastening holes 132 c as shown in FIG. 4 . The fastening holes 154 ofthe cover plate 150 are aligned with the fastening holes 132 c of themain body 130 respectively. With such configuration, the fasteningcomponents 170 penetrate the fastening holes 154 of the cover plate 150and the fastening holes 132 c of the main body 132 and then are fastenedto the top surface of the main conduit 110 as shown in FIG. 6 . Thereby,the main body 132 can be fixed onto the top surface of the main conduit110 by using the cover plate 150 of the gas injection device 100 and thesame fastening components 170 for fixing the cover plate 150, withoutusing any additional fasten means.

In some embodiments, the gas injection device 100 may further include acover lid 160 disposed on the cover plate 150. The cover lid 160 coversat least a part of the cap portion 136 of the grounding cap module 130as shown in FIG. 5 for fixing the cap portion 136 and the frame portion134 in the through hole 152. In one of the implementations, the coverlid 160 may include a plurality of fastening holes 164. Correspondingly,the cover plate 150 may also include a plurality of fastening holesaligned with the fastening holes 164 respectively. With suchconfiguration, the fastening components 170 penetrate the fasteningholes 164 of the cover lid 160 and the corresponding fastening holes ofthe cover plate to fasten the cover lid 160 onto the cover plate asshown in FIG. 6 . Thereby, with the cover lid 160 at least partiallycovering the cap portion 136 of the grounding cap module 130, the capportion 136 and the frame portion 134 can be fixed in the through hole152 without using any additional fasten means. Moreover, the cap portion136 can be simply placed on the frame portion 134 without any adhesiveor fasten means disposed therebetween, and the positions of the capportion 136 and the frame portion 134 can be fixed in the through hole152 by simply fastening the cover lid 160 onto the cover plate 150.Therefore, the assembling process and the components of the groundingcap module 130 can be simplified.

In some embodiments, the cover lid 160 may include a window opening 162,which exposes a part of the cap portion 136. In some embodiments,originally, the window opening 162 of the cover lid 160 is configured toexpose the optical window 140, and, now that the optical window 140 iscovered by the cap portion 136, the window opening 162 is configured toexpose a part of the cap portion 136 as shown in FIG. 6 . In the presentembodiment, the size of the window opening 162 is substantially smallerthan the size of the cap portion 136. In the embodiments of the shapesof the window opening 162 and the cap portion 136 being circular, thediameter of the window opening 162 is substantially smaller than thediameter of the cap portion 136. Thereby, the cover lid 160 can stillpartially cover the cap portion 136 to keep the cap portion 136 and theframe portion 134 in the through hole 152 without using any additionalfasten means.

As such, the grounding cap module 130 in the disclosure can resolve theissue of polymer residue accumulating on the top surface 114 of the mainconduit 110 without altering the original configuration of the gasinjection device 100 and using any additional fasten means. Therefore,yield rates of the etching process performed by the etching apparatus 10can be improved and the assembling process and the components of thegrounding cap module 130 are also simplified.

In accordance with some embodiments of the disclosure, a grounding capmodule includes a main body, a frame portion, and a cap portion. Themain body includes a first opening penetrating the main body and agrounding portion disposed on a periphery of the main body andconfigured to be electrically grounded. The frame portion is disposed onthe main body and includes a second opening aligned with the firstopening. The cap portion is disposed on the frame portion and covers thesecond opening, wherein the first opening, the second opening and thecap portion define a receiving cavity.

In accordance with some embodiments of the disclosure, a gas injectiondevice includes a main conduit, a gas pipe, an optical window, and agrounding cap module. The main conduit includes a gas inlet. The gaspipe is connected to the gas inlet to inject process gas into the mainconduit, wherein the gas pipe are electrically grounded. The opticalwindow is disposed on a top surface of the main conduit, wherein the topsurface is located above the gas inlet. The grounding cap module isdisposed on the top surface and includes a receiving cavity forreceiving and covering the optical window and a grounding portionconnected to the gas pipe to be electrically grounded.

In accordance with some embodiments of the disclosure, an etchingapparatus includes an etching chamber and a gas injection device. Theetching chamber defines a chamber cavity. The gas injection deviceincludes a main conduit, a gas pipe, an optical window, and a groundingcap module. The main conduit is connected to the etching chamber. Thegas pipe is connected to the main conduit to inject process gas therein,wherein the gas pipe is electrically grounded. The grounding cap moduleis disposed on a top surface of the main conduit and includes agrounding portion connected to the gas pipe to be electrically grounded.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A gas injection device for an etching apparatus,comprising: a main conduit comprising a gas inlet; a gas pipe connectedto the gas inlet to inject process gas into the main conduit, whereinthe gas pipe is electrically connected to a ground electrode; an opticalwindow disposed over the main conduit and above the gas inlet; and agrounding cap module covering the optical window and comprising: a mainbody disposed on a top surface of the optical window and comprising afirst opening penetrating the main body and a grounding portionconnected to the gas pipe; a frame portion disposed on the main body andcomprising a second opening aligned with the first opening; and a capportion disposed on the frame portion and covering the second opening,wherein the first opening, the second opening and the cap portion definea receiving cavity for receiving and covering the optical window.
 2. Thegas injection device as claimed in claim 1, further comprising a coverplate disposed on the main body and fixed to the main conduit, whereinthe cover plate comprises a through hole, and the cap portion and theframe portion are fitted in the through hole.
 3. The gas injectiondevice as claimed in claim 2, further comprising a plurality offastening components penetrating the main body and the cover plate tofix the main body and the cover plate onto the top surface of the mainconduit.
 4. The gas injection device as claimed in claim 2, furthercomprising a cover lid disposed on the cover plate and covering the capportion.
 5. The gas injection device as claimed in claim 4, wherein thecover lid comprises a window opening exposing a part of the cap portion,and the size of the window opening is substantially smaller than thesize of the cap portion.
 6. The gas injection device as claimed in claim1, wherein materials of the grounding cap module comprise metal.
 7. Anetching apparatus, comprising: an etching chamber defining a chambercavity; and a gas injection device comprising: a main conduit connectedto the etching chamber; a gas pipe connected to the main conduit toinject process gas therein, wherein the gas pipe is electricallyconnected to a ground electrode disposed outside of the etching chamber;an optical window disposed over the main conduit and above the gasinlet; a grounding cap module covering the optical window andcomprising: a main body disposed on a top surface of the optical windowand comprising a first opening penetrating the main body and a groundingportion connected to the gas pipe; a frame portion disposed on the mainbody and comprising a second opening aligned with the first opening; anda cap portion disposed on the frame portion and covering the secondopening, wherein the first opening, the second opening and the capportion define a receiving cavity for receiving and covering the opticalwindow.
 8. The etching apparatus as claimed in claim 7, furthercomprising a top electrode disposed on the etching chamber, and whereinand the process gas is introduced to the chamber cavity through the topelectrode.
 9. The etching apparatus as claimed in claim 7, wherein thegas injection device further comprises an optical window disposed on thetop surface, and the grounding cap module further comprises a receivingcavity for receiving and covering the optical window.
 10. The etchingapparatus as claimed in claim 9, wherein the grounding cap modulefurther comprises: a main body disposed on the top surface andcomprising a first opening penetrating the main body and the groundingportion protruded from an outer edge of the main body; a frame portiondisposed on the main body and comprising a second opening aligned withthe first opening; and a cap portion disposed on the frame portion andcovering the second opening, wherein the first opening, the secondopening and the cap portion define the receiving cavity.
 11. The etchingapparatus as claimed in claim 10, wherein the gas injection devicefurther comprises a cover plate disposed on the main body and fixed tothe main conduit, wherein the cover plate comprises a through hole, andthe cap portion and the frame portion are fitted in the through hole.12. The etching apparatus as claimed in claim 11, wherein the gasinjection device further comprises a cover lid disposed on the coverplate and covering the cap portion.
 13. A gas injection device for anetching apparatus, comprising: a main conduit; a gas pipe connected tothe main conduit to inject process gas into the main conduit, whereinthe gas pipe is electrically connected to a ground electrode; an opticalwindow disposed over the main conduit and above the gas pipe; and agrounding cap module covering the optical window and comprising areceiving cavity disposed at a central region of the grounding cap forreceiving the optical window and a grounding portion protruded from anouter edge of the central region and connected to the ground electrodethrough the gas pipe.
 14. The gas injection device as claimed in claim13, wherein the grounding cap module further comprises: a main bodydisposed on a top surface of the optical window and comprising a firstopening penetrating the main body and the grounding portion; a frameportion disposed on the main body and comprising a second openingaligned with the first opening; and a cap portion disposed on the frameportion and covering the second opening, wherein the first opening, thesecond opening and the cap portion define the receiving cavity.
 15. Thegas injection device as claimed in claim 14, further comprising a coverplate disposed on the main body and fixed to the main conduit, whereinthe cover plate comprises a through hole, and the cap portion and theframe portion are fitted in the through hole.
 16. The grounding capmodule as claimed in claim 14, wherein the frame portion is in a ringshape.
 17. The gas injection device as claimed in claim 15, furthercomprising a plurality of fastening components penetrating the main bodyand the cover plate to fix the main body and the cover plate onto thetop surface of the main conduit.
 18. The gas injection device as claimedin claim 15, further comprising a cover lid disposed on the cover plateand covering the cap portion.
 19. The gas injection device as claimed inclaim 18, wherein the cover lid comprises a window opening exposing apart of the cap portion, and the size of the window opening issubstantially smaller than the size of the cap portion.
 20. The gasinjection device as claimed in claim 13, wherein the grounding portioncomprises a fastening hole for a fastening component to penetratetherethrough and lock the grounding portion to the gas pipe.